Where are all the modular homes in western U.S.?

Can anyone explain to me why modulars are so common back east but nearly unheard of out here on the west coast? I guess there are some manufacturers ow but very few and far between. Its changing but slowly. How did this happen and why? Does anyone see this changing more rapidly in the near future? Drives me nuts! I'm envious of builders back east. I know about the Michelle Kaufman thing and a few others beginning to show up, but they are very expensive. Where are the manufacturers that build a product for $50-$80 per square foot like the ones back east?